Radiation cross-linked polyethylene is used as an insulation material in the wire and cable industry. Radiation curing of blends of polyethylene and diene rubber is disclosed as an alternative to chemical curatives in U.S. Pat. No. 4,104,210. Radiation cross-linked blends of polyethylene and EPDM rubber have been promoted for use in molded parts but they do not exhibit, even when containing cross-linking promotors, the tensile properties of chemically cross-linked blends. Radiation cross-linking of polymer blends offers processing advantages over chemically cross-linked blends and eliminates the use of chemical cross-linking agents which are expensive and may exhibit deleterious properties.